Preparation of extrusions of bulk mixed oxide compounds with high macroporosity and mechanical strength

Abstract

A simple and effective method for producing bulk single and mixed oxide absorbents and catalysts is disclosed. The method yields bulk single oxide and mixed oxide absorbent and catalyst materials which combine a high macroporosity with relatively high surface area and good mechanical strength. The materials are prepared in a pellet form using as starting compounds, calcined powders of the desired composition and physical properties these powders are crushed to broad particle size distribution, and, optionally may be combined with an inorganic clay binder. The necessary amount of water is added to form a paste which is extruded, dried and heat treated to yield and desired extrudate strength. The physical properties of the extruded materials (density, macroporosity and surface area) are substantially the same as the constituent powder is the temperature of the heat treatment of the extrudates is approximately the same as the calcination temperature of the powder. If the former is substantially higher than the latter, the surface area decreases, but the macroporosity of the extrusions remains essentially constant.

What is claimed is: 
     
       1. A method of preparing bodies of bulk metal oxide-based solid catalysts and absorbents having controllable surface area greater than 5 m 2  /g, macroporosity, high pore volume and, comprising the steps of: a compressive crush strength in the range of approximately 1-10 lb/mm.;   preparing a citrate precursor having, in desired proportions, metals selected from the group consisting of aluminum, zinc, transition metals, alkali metals, alkaline earth elements, rare earth elements and mixtures thereof;   calcining the citrate precursor at a temperature ranging between 550° C.-850° C. for approximately 4-8 hours to yield a highly dispersed and macroporous metal oxide solid;   treating the metal oxide solid by crushing and sizing to yield a highly dispersed, macroporous powder having a continuous particle size distribution such that fine and coarse size particles are retained, and macropores, in the size range of 0.1 μm to 25 μm in diameter, comprise a least 60% of the total pore volume of the powder and the remaining pores have a diameter less than 0.1 μm;   adding about 2-7 percent by weight of a clay binder material to the powder;   forming solid bodies from the powder;   shaping the bodies to an appropriate size and shape;   drying the bodies in air at 100° C.-120° C. for approximately 16 hours; and   heat treating the bodies for approximately 2-6 hours at a temperature in the range of approximately 650° C.-850° C.   
     
     
       2. The method of claim 1 wherein the metal oxide powder has a particle size distribution such that approximately 10 to 35% of the particles have a size ranging from 125-210 μm, 10-35% of the particles have a size ranging from 90-124 μm, 5-20% of the particles have a size ranging from 75-89 μm, 5-15% of the particles have a size ranging from 63-74 μm and 25-50% of the particles are of a size less than 63 μm. 
     
     
       3. The method of claim 1 wherein said clay binder material is bentonite. 
     
     
       4. The method of claim 2 wherein the metal oxide powder is formed from a metal selected from the group consisting essentially of copper, iron, aluminum, zinc, titanium and mixtures thereof. 
     
     
       5. The method of claim 4 wherein the metal oxide powder is selected from the group consisting of oxide compounds of copper, iron, aluminum and mixtures thereof. 
     
     
       6. The method of claim 5 wherein the atomic ration of the metals is xCu:yFe;zAl, wherein x is between 1 and 5, y is between 0 and 6, and z is between 0.5 and 6. 
     
     
       7. The method of claim 4 wherein the metal oxide powder is selected from the group consisting of oxide compounds of copper, aluminum and mixtures thereof. 
     
     
       8. The method of claim 7, wherein the atomic ratio of the metals is xCu:yAl wherein x and y are each between 1 and 3. 
     
     
       9. The method of claim 4 wherein the metal oxide powder is selected from the group consisting of oxides of zinc, titanium and mixtures thereof. 
     
     
       10. The method of claim 9 wherein the atomic ratio of the metals is xZn:yTi wherein x is 0.4-2 and y is 0-2. 
     
     
       11. The product produced by the method of claim 1. 
     
     
       12. The product of claim 11, wherein the product is an active sorbent catalyst for gas cleanup. 
     
     
       13. The product of claim 11, wherein the product is a regenerable hot gas desulfurization sorbent. 
     
     
       14. An extruded sorbent composition comprising mixed oxide compounds of xCuO, yFe 2  O 3  and zAl 2  O 3 , wherein x is 1-5, y is 0-6 and z is 1-6, and 2-7 percent by weight of a clay binder material, said extruded sorbent having a high degree or porosity ranging between 60 and 85%, such that at least 60 percent of the pores have a diameter ranging from approximately 0.1 to 25.0 μm, the remaining pores have a diameter less than 0.1 μm and wherein said extruded sorbent composition has a surface area greater than about 5 m 2  /g and a compressive crush strength in the range of approximately 1-10 lb/mm. 
     
     
       15. An extruded sorbent composition comprising mixed oxide compounds of xCuO and yAl 2  O 3 , wherein x and y are between 1 and 3, and 2-7 percent by weight of a clay binder material, said extruded sorbent having a high degree of porosity, ranging between 60% and 85%, such that at least 60% of the pores have a diameter ranging from approximately 0.1 μm to 25.0 μm, the remaining pores have a diameter less than 0.1 μm and wherein said extruded sorbent composition has a surface area greater than 5 m 2  /g and a compressive crush strength in the range of approximately 1-10 lb/mm. 
     
     
       16. An extruded sorbent composition comprising mixed oxide compounds of xZnO and yTiO 2 , wherein x is 0.4-2 and y is 0-2, and about 2-7 percent by weight of a clay binder material, said extruded sorbent having a high degree of porosity, ranging between 60 and 85%, such that at least 60 percent of the pores have a diameter ranging from approximately 0.1 to 25 μm, the remaining 40% of the pores have a diameter less than 0.1 μm, and wherein said extruded sorbent composition has a surface area greater than 5 m 2  /g and a compressive crush strength in the range of approximately 1-10 lb/mm.